半导体导论 P124-125
CHAPTER 3 The Semiconductor in Equilibrium
(d) T = 400 K, N d = 0, N a = 1014 cm-3
(e) T = 500 K, N d = 1014 cm-3, Na = 0
3.37 Repeat problem 3.36 for GaAs.
3.38 Assume that silicon, germanium, and gallium arsenide each have dopant concentrations of Nd = 1X1013 cm-3 and Na = 2.5 x 1014 cm-3 at T=300K.For each of the three materials(a) Is this material n type or p type?(b) Calculate n0 and p0.
3.39 A sample of silicon at T =450K is doped with boron at a concentration 0f 1.5x1015 cm-3and with arsenic at a concentration of 8 X 1014 cm-3 .(a) Is the material n type or p type? (b) Determine the electron and hole concentrations .(c) Calculate the total ionized impurity concentration.
3.40 The thermal equilibrium hole concentration in silicon at T = 300 K is p0=2x1015cm-3.Determine the thermal-equilibrium electron concentration .Is the material n type or p type?
3.41 In a sample of GaAs at T = 200 K, we have experimentally determined that n0 = 5 p0 and that Na = 0. Calculate n0, p0, and N d.
3.42 Consider a sample of silicon doped at N d = 1014 cm-3 and Na = 0 Calcu1ate the majority-carrier concentration at (a) T = 300 K, (b) T = 350 K,(C ) T = 400 K (d) T = 450 K, and (e) T = 500 K.
3.43 Consider a sample of silicon doped at N d= 0 and Na = 1014cm-3 .Plot the majority-carrier concentration versus temperature over the range 200≤T≤500K.
3.44 The temperature of a sample of silicon is T = 300 K and the acceptor doping concentration is Na = 0. Plot the minority-carrier concentration (on a log-log plot) versus Nd over the range 1015≤N d≤1018 cm-3.
3.45 Repeat problem 3.44 for GaAs.
3.46 A particular semiconductor material is doped at N d = 2 x 1013 cm-3, Na = 0, and the intrinsic carrier concentration is ni = 2 x 1013 cm-3. Assume complete ionization. Determine the thermal-equilibrium majority-and minority-carrier concentrations.
3.47 (a) Silicon at T = 300 K is uniformly doped with arsenic atoms at a concentration of 2 x 1016 cm-3 and boron atoms at a concentration of 1 x1013 cm-3. Determine the thermal-equilibrium concentrations of majority and minority carriers.
(b) Repeat part (a) if the impurity concentrations are 2 x1015 cm-3 phosphorus atoms and 3 x 1016 cm-3 boron atoms.
3.48 In silicon at T = 300 K, we have experimentally found that n0=
4.5 x 104 cm-3and N d=5x1015cm-3. (a) Is the material n type or p type? (b) Determine the majority and minority-carrier concentrations. (c) What types and concentrations of impurity atoms exist in the material?
Section 3.6 Position of Fermi Energy Level
3.49 Consider germanium with an acceptor concentration of Na = 1015 cm-3 and a donor concentration of N d = 0. Consider temperatures of T = 200, 400,and 600 K. Calculate the position of the Fermi energy with respect to the intrinsic Ferrni level at these temperatures.
3.50 Consider germanium at T = 300 K with donor concentrations of N d= 104, 1016and1018 cm-3 .Let Na = 0. Calculate the position of the Fermi energy level with respect to the intrinsic Fermi level for these doping concentrations.
3.51 A GaAs device is doped with a donor concentration of 3X1015cm-3 .For the device to operate properly ,the intrinsic carrier concentration must remain less than 5 percent of the total electron concentration .What is the maximum temperature that the device may operate?
3.52 Consider germanium with an concentration of Na=1015cm-3and a donor concentration of N d=0.Plot the position of the Fermi energy with respect to the intrinsic Fermi level as a function of temperature over the range 200 ≤T ≤600 K.
3,53 Consider silicon at T =300K with Na=0. Plot the position of the Fermi energy with respect to the intrinsic Fermi level as a function of the donor doping concentration over the range 1014≤N d≤1018cm-3.
3.54 For a particular semiconductor,Eg=1.50eV,m*p=10m*n，T=300K，and ni=105cm-3. (a)Determine the position of the intrinsic Fermi energy level with respect to the center of the bandgap. (b)Impurity atoms are added so that the Fermi energy level is 0.45eV below the center of the bandgap .(i)Are acceptor or donor atoms added? (ii)What is the concentration if impurity atoms added?
3.55 Silicon at T = 300 K contains acceptor atoms at a concentration of Na = 5 x1015cm-3 . Donor atoms are add forming an n-type compensated semiconductor such that the Fermi level is 0.215 eV below the conduction band edge .What concentration of donor atoms are added?
3.56 Silicon at T = 300 K is doped with acceptor atoms at a concentration of Na = 7 x1015cm-3. (a) Determine E f-E v. (b) Calculate the concentration of additional acceptor atoms that must be added to move the Fermi level a distance kT closer to the
